I am from the UK and had a similar problem on a Porsche 911 although it had 4000 miles on the clock the dealer was helpful, I think you should insist to get a replacement car, its only done 400 miles for God`s sake they could easily put the new gearbox in and use it as a demo or easily sell it on their own forecourt without the new owner even knowing, I would even speak to Chrysler yourself. Who is the dealer?

On a better note you will enjoy your new crossfire, watch it turn heads!